Thin-film radiative thermal diode with large rectification

TL;DR

This paper introduces a novel thin-film radiative thermal diode that significantly improves heat flow rectification by using metal-insulator transition materials and polar dielectrics, achieving over 140-fold rectification at nanoscale gaps.

Contribution

It presents a new design for radiative thermal diodes utilizing thin films of vanadium dioxide and cubic boron nitride, with a theoretical rectification ratio over 140, surpassing previous methods.

Findings

Rectification ratio over 140 achieved at ~100 nm gaps.

Design is robust and easy to fabricate with flexible material choices.

The approach significantly outperforms existing thermal diode technologies.

Abstract

We propose a mechanism to substantially rectify radiative heat flow by matching thin films of metal-to-insulator transition materials and polar dielectrics in the electromagnetic near field. By leveraging the distinct scaling behaviors of the local density of states with film thickness for metals and insulators, we theoretically achieve rectification ratios over 140-a 10-fold improvement over the state of the art-with nanofilms of vanadium dioxide and cubic boron nitride in the parallel-plane geometry at experimentally feasible gap sizes (~100 nm). Our rational design offers relative ease of fabrication, flexible choice of materials, and robustness against deviations from optimal film thicknesses. We expect this work to facilitate the application of thermal diodes in solid-state thermal circuits and energy conversion devices.